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phty251 > 5 senses > Flashcards

5 senses Flashcards

1
Q

visible light range

A

400 - 750nm (blue - red)

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2
Q

role of optical component of the eye?

A

collects and focuses light onto the plane of the retina

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3
Q

role of neural component of the eye?

A

converts light energy into patterned changes of membrane potential that the brain can decode

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4
Q

refractive power of the eye

A

approximately 60 diopters

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5
Q

focal point of eye based on the approximate refractive power

A

approximately 17mm beyond the lens

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6
Q

what are the 3 processes of the near response?

A

Accommodation, constriction, convergence

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7
Q

what is the activity of parasympathetic on ciliary muscles/zonular fibres/lens when looking at distant objects?

A

low parasympathetic activity therefore ciliary muscle relaxed, and zonular fibres are pulled taut which flattens the lens

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8
Q

what is myopia and its treatment?

A

NEARSIGHTEDNESS eyeball too long, therefore, light focused ahead of the plane of the retina, corrected using convex lens

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9
Q

what is hypermetropia and its treatment?

A

FARSIGHTED, eyeball too short, objects focused beyond scope of retina. corrected with convex lens, which increases focal power to bring focal point forward

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10
Q

what is astigmatism and its treatment?

A

curvature of cornea and/or lens is aspherical, therefore different amount of refraction in different planes. corrected with cylindrical lens

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11
Q

what is presbyopia and its treatment?

A

age-related loss of accommodation. Lens lose elasticity, as a consequence near point recedes from approx. 10cm at 20 years to 80cm at 60 years. corrected with convex (reading glasses)

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12
Q

what is cataract?

A

lens becomes opaque due to cells within lens dying. lens can be surgically removed and replaced with plastic one. ability to accommodate is lost post-surgery.

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13
Q

constriction of the pupil - dilated

A
  • decreased periphery

- when object is close

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14
Q

constriction of pupil - undilated

A
  • increased periphery

- object further away

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15
Q

what is accommodation in near response?

A

contraction/relaxation of ciliary muscle to alter lens shape and change refractive power

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16
Q

what is constriction of pupil?

A

improved depth of focus, fewer optical abberations including edges of lens

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17
Q

what is convergence of eyes?

A

objects remain in register on corresponding parts of the two retinae

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18
Q

what is the retina important?

A

the retina is part of the brain, contains photoreceptors at the back and ganglion cells and axons in front for processing.

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19
Q

how does info flow between photorecptors and ganglion cells?

A

via interneurons

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20
Q

function of rods (photoreceptor) and their approximate number per retina?

A
  • function in low-level light (night vision)
  • not colour sensitive
  • 120 million per retina
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21
Q

function of cones (photoreceptor) and their approximate number per retina?

A
  • function in high light levels (day/twilight vision)
  • 8 million per retina
  • 3 types: red, blue and green
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22
Q

what makes photoreceptors light sensitive?

A

the presence of photopigments

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23
Q

the 2 components of the photopigment

A
  1. ) a membrane-spanning protein called opsin
    - rods have rhodopsin
    - cones have S, M, or L photopsin
  2. ) a chromophore called retinal (vitamin A derivative)
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24
Q

what colour is S photopsin?

A

Blue

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25
Q

what colour is M photopsin?

A

green

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26
Q

what colour is L photopsin?

A

Red

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27
Q

phototransduction in the dark

A
  • retinal is non-activated (inactive 11-sic isoform)
  • intracellular cGMP is high
  • cGMP gated channels open
  • Na influx into blood cells
  • photoreceptor (rods) depolarized to - 30mV
  • lots of glutamate released onto bipolar cells
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28
Q

phototransduction in the light

A
  • light energy/photons
  • retinal changed to active all-trans isoform
  • trans- retinal activates a G protein called transducin
  • transducin activates cGMP phosphodiesterase, breaking down cGMP to normal GMP
  • less cGMP therefore cGMP gated channels close
  • photoreceptor hyperpolarised to - 60mV
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29
Q

consequences of vitamin A deficiency

A
  • night blindness/ eyes unable to adapt to low light conditions
  • severe problem in developing countries
  • 1st symptom is dry eyes
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30
Q

retinal processing

A
  • photoreceptors communicate with retinal interneurons via GRADED changes in membrane potential
  • retinal interneurons may be excitatory or inhibitory
  • retinal ganglion cells have long axons (form optic nerve), fire AP, and send visual info to centres in brain for visual processing
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31
Q

at night, intracellular cGMP levels are…?

A

cGMP levels high at night

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32
Q

when do cGMP channels open?

A

cGMP gated channels open in absence of light

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33
Q

when is retinal activated? (active c11-cis isoform)

A

retinal is activated with the presence of light

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34
Q

what happens when cGMP gated channels open?

A

Na influx, photoreceptor depolarised, and lots of glutamate released onto bipolar cells

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35
Q

S-photopsin

A

blue, most sensitive to short wavelengths

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36
Q

M- photopsin

A

green, sensitive to medium wavelengths

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37
Q

L- photopsin

A

red, sensitive to long wavelengths

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38
Q

4 common diseases that cause damage to optic nerve or retina

A
  • glaucoma
  • diabetes
  • alzheimers
  • parkinsons
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39
Q

what causes inherited colour blindness?

A

genes encoding the M and L opsins are on the X chromosome.

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40
Q

what is the ‘blind spot’?

A

the optic disc where axons leave retina, no photoreceptors at this point.

41
Q

what is sound?

A

pressure waves in the atmosphere

42
Q

frequency/pitch range of human hearing

A

between 20 and 2000Hz

43
Q

threshhold of human hearing approximate start and ‘end’

A

0 and 145 dB. decible scale = log scale.

44
Q

3 parts of inner ear

A
  • cochlea
  • semicircular canals
  • vestibule
45
Q

3 parts of outer ear

A
  • auricle
  • external auditory canal
  • tympanic membrane
46
Q

ossicles of middle ear

A
  • stapes
  • incus
  • malleus
47
Q

What parts of the ear are air-filled?

A

inner and outer ear are air-filled.

48
Q

how does sound transduction work from outer to middle ear?

A
  • sound waves cause the tympanic membrane to vibrate

- vibrations are then transmitted via the ossicles

49
Q

what happens to the vibrations after they are transmitted via the osscicles?

A
  • vibrations then cause a change in P in fluid of scala vestibuli
  • this fluid displacement causes displacement in cochlear duct
50
Q

what does the displacement in the cochlear duct then cause?

A
  • a displacement in the basilar membrane thus the organ of corti
51
Q

what does a displacement in the basilar membrane/organ of corti create?

A

creates shear forces, forcing the stereocilia on hair cells to bend

52
Q

deflection of stereocilia causes…

A
  • opening of chemically gated ion channels

- K+ enters hair cells from endolymph causing depolarization

53
Q

(depolarization once K+ has entered hair cell causes…

A
  • depolarization opens Ca2+ channels and Ca2+ enters hair cell
54
Q

increased concentration of Ca2+ in hair cell causes…

A
  • increased Ca2+ causes neurotransmitter release onto the cochlear nerve
55
Q

what happens after neurotransmitter release on cochlear nerve?

A
  • synapse on cochlear nucleus in brainstem
  • axons project through lateral lemniscus to medial geniculate body
  • axons then project to primary auditory cortex (R & L)
56
Q

how is pitch/frequency discrimination determined?

A

discrimination of pitch is determined by activity in hair cells at specific points on basilar membrane

57
Q

how is intensity of sound determined?

A

loudness is determined in the number of impulses per second in auditory nerve fibres (change in depolarisation causes change in Ca2+ influx and consequent vesicle release)

58
Q

deafness by infection is caused by ?

A

build up of fluid which dampens tympanic membrane and prevents correct sound transmission

59
Q

what is conduction deafness?

A

impaired sound transmission through outer or middle ear

60
Q

where on basilar membrane do hair cells respond to high frequency?

A

at base of basilar membrane, where hair cells are taught

61
Q

where on basilar membrane do hair cells respond to low frequency?

A

at apex of basilar membrane where hair cells are loose

62
Q

what is the stimuli of the vestibular system?

A

stimuli is angular and linear accelerations of head

63
Q

what are the 5 vestibular receptors in each ear?

A
  • 3 x semicircular canals

- 2 x otolith organs

64
Q

what do semicircular canals transduce?

A

semicircular canals rotational accelerations of head

65
Q

what do otolith organs transduce?

A

otolith organs transduce linear accelerations of the head

66
Q

what do the horizontal semicircular canals detect?

A

horizontal semicircular canals detect shaking of head in TRANSVERSE plane

67
Q

what do anterior semicircular canals detect?

A

anterior semicircular canals detect nodding in SAGGITAL plane

68
Q

what do posterior semicircular canals detect?

A

posterior semicircular canals detect rotation in CORONAL plane

69
Q

what is the ampulla and where is it located?

A

the ampulla is the dilated end of a semicircular duct in a semicircular canal.

70
Q

describe the cupula

A

the cupula is a gelatinous structure that sits in the ampulla which holds the hair cell and stereocilia in place

71
Q

what happens in left side semicircular canals when head moves in left direction? (vv)

A

when left moves to left, the hair cells are bent towards the tallest end,

72
Q

moving left causes endolymph in ampulla to move….

A

moving left causes endolymph to move right

73
Q

when head moves in the opposite direction to semicircular canal side it causes…

A

moving in opposing direction causes bending toward the smallest stereocilia.

74
Q

what does bending toward the tall end of stereocilia cause?

A

towards tall end opens mechanically gated ion channels thus depolarization (stimulation)

75
Q

what does bending toward the short end of stereocilia cause?

A

towards short end shuts mechanically gated ion channels thus hyperpolarization (inhibition)

76
Q

what does the resting discharge rate of the vestibular nerve allow?

A

detect increase/decreases in AP firing thus hair cells can signal in 2 directions.

77
Q

what is the orientation of the utricle and its hair cells when standing?

A

utricle is approximately horizontal, and its hair cells within it are oriented vertically

78
Q

what is the orientation of the saccule and its hair cells when standing?

A

saccule is approximately vertical, and its hair cells within are oriented horizontally

79
Q

what does the movement of otoconia cause?

A

movement of otoconia causes bending of hair cells

80
Q

what is the central vestibular pathway?

A
  • central vestibular pathway: axons project to vestibular nuclei in brain stem
  • info then used to stabilise eyes, head and maintain balance
81
Q

what does the oculomotor nucleus do?

A

oculomotor nucleus stabilises images on the retina

82
Q

What is an acoustic neuroma?

A

abnormal growth of schwann cells

83
Q

what is motion sickness and how do you treat it?

A
  • a mismatch between visual and vestibular info

- treated with MeclozineHydrochloride (sea legs)

84
Q

what is vertigo?

A

disease affecting the vestibule or its afferent fibres

85
Q

what is ‘bedspins”?

A
  • alcohol/ethanool infiltrates cupula and lowers density causing it to float, thus bending hair cells.
86
Q

what are taste buds made up of?

A

complex cluster of 50-100 columnar epithelial cells (type 1, 2 and 3)

87
Q

type 1 columnar epithelial cells in taste bud

A

glial cells, maintain homeostasis

88
Q

type 2 columnar epithelial cells in taste bud

A

umami, sweet, bitter

89
Q

type 3 columnar epithelial cells in taste bud

A

sour, salty

90
Q

taste buds are innervated by what nerves?

A
  • chorda tympani
  • lingual
  • trigemina
  • glossopharyngeal nerves
91
Q

where do the afferent fibres of the tastebud nerves synapse? (what happnens after?)

A

synapse in medulla

info is then relayed to the thalamus then to cortex

92
Q

what taste cells have G-protein mediated signal transduction pathways? (draw it out)

A

type 2 taste cells have G-protein mediated signalling

sweet, bitter, umami

93
Q

structure of sweet taste receptor?

A

homodimer or type 1 receptor

94
Q

structure of bitter taste receptor?

A

monomer of type 2 receptor

95
Q

structure of umami taste receptor?

A

heterodimer of type 1 receptor

96
Q

what taste cells require Non G -protein signalling transduction pathways? (draw it out?)

A

type 3 cells have non G protein signaling

sour and salty

97
Q

where does olfactory signal transduction occur?

A

olfactory signal transduction occurs in receptor cilium of olfactory cells

98
Q

what enzyme embedded in plasma membrane of olfactory cilia is activated upon inhalation/entry of odourant?

A

adenylyl cyclase is activated.

phty251 (6 decks)

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